I fronted bands for years, so I've thought a lot about this. From my experience, I've noticed that you might be able to keep your tone and range for many years if you don't push through a blown voice night after night, but you're eventually going to realize that you can't have the resiliency of a twenty eight year old voice for your entire career. Back then, i could sing at practice six nights a week for hours each time. By 35, i improved and expanded some of my abilities, but three hour shows two nights in a row became more difficult. We weren't famous, so i was able to take breaks in between shows. If i did a really long recording session, i could rest my voice for a couple days. Some singers don't get to do that. Even on a blown voice day, there are little things you can do to make it happen, but if you work a blown voice into passable singing too often, you can do permanent damage. The schedules singers keep are brutal, and you can be a cold or a bad vocal mix away from messing your voice up for a while or worse.
I don't think that an engineer fixed a sour note of mine with autotune, but we did punch in multiple takes for records. I did not have a live backing track at our shows. However, if i were on tour right now at my age playing five nights in a row, would i cut a good track of the show just in case? Depends. I wouldn't want to do that, but i also wouldn't sacrifice my voice for the rest of my life just to keep it real for one night.
I pushed through multiple times, but i still have most of my voice. I have been working it back into shape lately for fun and for the calming effect of it. I might sing again publicly someday, but I'm doing other things right now. Do i like backing live tracks over pure live? Not really. Can i say that i would have never used one in a pinch if singing was my main job? Not if I'm being honest.